I. FIELD OF THE INVENTION
This invention is in the general field of temperature control and indicating systems;
The invention is more particularly directed to thermocouples used for temperature control and indicating;
The invention is more directly in the field of thermocouples wherein an outer thermocouple shield is formed of one of the two dissimilar thermocouple metals In one of several variations of this invention I use two concentric cylindrical members, each made of one of the two dissimilar metals. This particular variation has some very interesting qualities since a great area is involved for each of the two dissimilar metals increasing the response of the potential created by the heat to which they are subjected in use resulting in a thermocouple system having faster response, greater accuracy, more reliability, and longer useful life than systems heretofore in use. In another variation I utilize a first thermocouple member of the first of the two thermocouple metals with successive coatings of various materials including one coating of the second of the two thermocouple materials. In all of the variations of this invention a basic innovative feature is the use of one of the thermocouple metals surrounding the other thermocouple metal with additional protective and enhancing features.
II. Description of the Prior Art
Thermocouples are well known and in wide use. There have been so many thermocouple systems devised that it would be futile to attempt to list them in detail. However, I do not know of any thermocouple where one of the two dissimilar thermocouple metals surrounds the other of the two dissimilar thermocouple metals to create the electrical potential difference to determine the temperature as I have done in this invention. I have provided other improvements as well which will be detailed below.
Thermocouples are widely used to sense temperatures, particularly high temperatures. Thermocouples generally operate by sensing an electrical potential generated between two connected wires of dissimilar materials when subjected to temperature variations. The electrical potential generated is then converted to an indication of actual temperature as is known to those skilled in the art.
A basic thermocouple normally consists of a hollow, bullet shaped metallic shield with two dissimilar metallic connected wires within the shield. A glass seal or the like seals around the open end of the shield and also seals around the wires.
The interior of the thermocouple is packed with insulation material. The insulation is necessary to prevent the two wires from shorting at a position other than their one connection at one end of each wire. However, the insulation is also a major problem. The insulation reduces the sensitivity of the instrument. Additionally, the seal will randomly crack on cooling. When this occurs, the result can be the introduction of moisture into the insulation. Moist insulation contaminates the wires and their connection to each other (referred to as xe2x80x9cpoisonedxe2x80x9d by those skilled in the art) and reduces sensitivity and may short the two wires.
With my invention, there is no longer a need for insulation. I accomplish this by forming the shield from one of the two dissimilar metals used to make a thermocouple work. I then attach a wire formed of the second of the two dissimilar metals to the interior of the bullet shaped shield. There is no requirement for insulation, thus the poisoning and other problems caused by the insulation are eliminated.
Being constructed in this manner my new thermocouple may be filled with an inert gas, the interior may be vacuumed, the shield may be coated inside and/or outside, or the interior of the shield may even be left open to the atmosphere. The wire inside the shield may be stretched tight to provide maximum sensitivity and accuracy.
In one interesting variation of my invention I form a thermocouple of two dissimilar metallic concentric tubes. One of the tubes is formed of the first of two dissimilar metals and the second tube is formed of the second of the two dissimilar metals. This provides for a large and uniform surface of each metal resulting in interesting time, sensitivity, and magnitude of response when the tubes are subjected to heat.
In what is, perhaps, the most innovative, useful and unique variation of my basic premise for thermocouples, I commence by forming a wire or the like made of the first of two thermocouple dissimilar metals. I then coat the wire or the like with a layer of non electrical conducting material, leaving a segment of the wire or the like not coated Next, I coat the non electrical conducting material and the not coated segment of wire or the like with a layer of the second of the two thermocouple metals. Now, I may, but am not required to, coat the entire wire with its previously recited coatings with a layer of corrosion resistant material or the like. Finally, by using clamps or other means clear to those skilled in the art I make an electrical contact to each of the two dissimilar thermocouple materials. These last mentioned two contacts are for connection to measuring instruments or the like.
It is an object of this invention to provide a thermocouple without insulation in the thermocouple shield;
Another object of this invention is to provide such a thermocouple which will be more sensitive and more accurate than previously known thermocouples;
Another object of this invention is to provide a thermocouple with a longer useful life than prior thermocouples:
Another object of this invention is to provide compact and miniature thermocouples of high sensitivity, long life, and maximum reliability.
The foregoing and other objects and advantages of this invention will become apparent to those skilled in the art upon reading the description of preferred embodiments, which follows, in conjunction with a review of the appended drawings.